1. Field of the Invention
This invention relates to a pickup lens suitable for mounting in a camera which uses a CCD or CMOS device as a pickup element.
2. Description of Related Art
One characteristic of this pickup lens is a short optical length. Another characteristic is that various aberrations thereof are corrected to amounts sufficiently small that distortion of the image formed by this pickup lens is not recognized by visual perception, and sufficiently small as to satisfy the requirements of the integration density of the pickup element. Below, “various aberrations are corrected to amounts sufficiently small that distortion of the image formed by this pickup lens is not recognized by visual perception, and sufficiently small as to satisfy the requirements of the integration density of the pickup element” is, for simplicity, represented by the phrase “various aberrations are satisfactorily corrected” or similar. An image for which various aberrations are satisfactorily corrected may be called “satisfactory image”.
A pickup lens mounted in a compact camera which uses a CCD or CMOS device as a pickup element must have a short optical length, and must be able to be manufactured at low cost. One such lens is, for example, the pickup lens disclosed in Japanese Patent Laid-open No. 11-38316. However, although the pickup lens disclosed in this publication comprises few components, which number four elements in four groups, the first lens, which is the initial lens approaching from the object side, is very thick and so difficult to machine. As a result, manufacturing costs are increased and productivity is poor. Moreover, the optical length exceeds 10 mm, so that the optical length is too long for a lens mounted in a compact camera which uses a CCD or CMOS device as a pickup element.
This invention has as an object the provision of a pickup lens in which various aberrations are satisfactorily corrected, which can be manufactured at low cost, and which has an optical length of 10 mm or less.